I want to read an Engine Coolant Temperature sensor using a voltage divider in the usual way on an arduino. I have already made similar readers. I am only concerned with interfering signals because the ECU is also reading this sensor directly, and with its own dedicated ground and signal wires.
This sensor dictates fuel trims and starting conditions based on engine temperature so it is pretty essential that its signal is not molested.
This sensor also shares ground with the airflow sensor (whose input it being used as an ethanol content analyzer), The EGR temp sensor input (utilized as a wideband sensor input), and the Throttle position sensor (as itself). All of these inputs impact fueling and could have annoying consequences if a little off, and catastrophic consequences if off by a lot, at the wrong time.
The pull-up resistors on this ecu are ~10kohms
So, the question is...
Can I use a normal voltage divider to read this temp sensor (thermistor) without any consequences?
I am mildly fearful that introducing 5v or 3.3v to read it voltage divider style will interfere with the ECU operation. I am hoping that someone with more expertise can chime in on this. Its not like a ohm meter that uses an isolated circuit. The car runs off on one battery...
Attached are some screenshots highlighting the important stuff if it helps. The red arrow points to the sensor I intend to measure or "splice" into.
